Bottom-up in situ formation of Fe3O4 nanocrystals in a porous carbon foam for lithium-ion battery anodes

A facile and scalable process for the in situ formation of Fe3O4 nanocrystals in a pre-formed carbon foam (CF) (Fe3O4/CF) was developed, which involved impregnation of an aqueous iron nitrate solution onto CF followed by controlled thermal treatment in an inert atmosphere. N-2 adsorption/desorption and BET measurements showed that the CF was a mesoporous carbon with a high pore volume and specific surface area. Transmission electron microscopy, scanning electron microscopy, X-ray diffraction measurement, thermogravimetric analysis, and X-ray photoelectron spectroscopy (XPS) revealed that 5-50 nm Fe3O4 nanocrystals at a high loading of 78.7 wt% were formed preferentially in the confined pores of CF. When tested for anode material in a Li ion half-cell, the Fe3O4/CF composite was far superior to unsupported Fe3O4 nanocrystals, exhibiting significantly improved Coulombic efficiencies and cycling stability and achieving >780 mA h g(-1) after 50 deep charge-discharge cycles with >95% cycling efficiency.